1. Field of the Invention
The present invention relates to a large-scale display device employing PTAs (plasma tube arrays).
2. Description of the Related Art
A gas discharge tube including a glass tube having a diameter of about 1 mm and filled with a discharge gas with opposite ends thereof sealed and a fluorescent layer provided on an interior surface of the glass tube is generally called “plasma tube”. A display panel including a multiplicity of such plasma tubes regularly arranged, a plurality of transparent display electrodes provided on a front side thereof as extending perpendicularly to the plasma tubes and data electrodes (address electrodes) provided on a back side thereof as extending parallel to the plasma tubes is generally called “plasma tube array (PTA)”. In the PTA, electric discharge is caused by applying given operating voltages to the display electrodes and the data electrodes, and vacuum UV radiation generated by the electric discharge excites a fluorescent material, which in turn emits visible light for display.
In principle, the size of the display device employing the PTAs is determined by the length and number of the plasma tubes. If a large-scale display panel is produced from a single PTA, however, it is difficult to transport the display panel from a plant into an installation site. To cope with this, a plurality of smaller-size PTA unit modules each having a smaller thickness and a light weight are produced, and assembled at the installation site to be connected to each other with the use of a module connection structure.
The PTA unit modules basically each have a screen size of about 1 m×1 m. The use of the PTA unit modules makes it possible to construct large-scale display devices having various screen sizes. Where six unit modules are arrayed in a 3×2 matrix, for example, the resulting display device has a screen size of 3 m×2 m. In this case, however, connection portions present between the PTA unit modules should be concealed in order to serve the unit modules as a single panel display device. A known method for concealing the connection portions is to minimize the width of the connection portions by keeping vertically aligned unit modules into abutment with each other (see, for example, JP-A-2006-164635).
A large-scale display device employing a plurality of flat display devices such as LCDs or PDPs instead of the PTAs is also known (see, for example, JP-A-9(1997)-130701). In the large-scale display device, the flat display devices each include a driving section disposed along one or two peripheral edges of a rectangular image display region thereof, and are arrayed so that peripheral edges thereof not provided with the driving sections abut with each other to make their seams inconspicuous and the driving sections are covered with the image display regions to be concealed.
Where the PTA unit modules abut with each other in the large-scale display device, however, ends of the plasma tubes abut against each other. This causes the ends of the glass tubes to be abraded by each other, so that the glass tubes are liable to be damaged to be broken. If the glass tube of a plasma tube is broken, the discharge gas is escaped from the plasma tube. Therefore, the electric discharge is no longer established in that plasma tube, so that a defect occurs on the display screen to significantly reduce the display quality.
Further, opposite end portions of the glass tube are closed with a sealing material for sealing the discharge gas in the plasma tube. Therefore, seal portions of the plasma tubes sealed with the sealing material are each defined as a non-display region in which the electric discharge does not occur. If the thickness of the seal portion is reduced to reduce the size of the non-display region, the probability of the escape of the discharge gas is correspondingly increased.